The AOA was established over 130 years ago to bring osteopathic medicine's unique philosophy of caring for the whole person to prevent, diagnose and treat illness, disease and injury to the forefront of traditional medicine. Headquartered in Chicago with an office in Washington, D.C., the AOA's mission is to advance the philosophy and practice of osteopathic medicine by promoting excellence in education, research, and the delivery of quality, cost-effective health care within a distinct, unified profession. Although osteopathic physicians are represented in all medical specialties, over 50% of DOs in active practice specialize in primary care, including family medicine, general internal medicine, pediatrics, and obstetrics and gynecology.